The present invention relates to vehicles with lean control systems. In particular, the present invention relates to vehicles with hydraulically-actuated primary and auxiliary lean control systems coupled to a vehicle leaning suspension system for enhancing vehicle stability.
Certain types of vehicles are unstable (e.g., more prone to rolling over) in certain modes of operation. For example, a three-wheeled vehicle that permits roll axis articulation may be unstable when the vehicle center of gravity is located above the roll axis. Under normal operation, many such instabilities are compensated for by using a closed loop control system (for example, an electro-hydraulic or electro-mechanical system) including or coupled to elements of the vehicle systems (for example, elements of the vehicle suspension system) which are actuatable in response to a signal from a control unit. Based on feedback to the control unit from vehicle system elements and sensors, signals from the control unit actuate the responsive vehicle system elements to stabilize the configuration of the vehicle. For example, vehicle lean control systems may cause the body of the vehicle to lean into a turn, thereby increasing the stability of the vehicle during turning.
In hydraulically-actuated lean control systems, the lean control system may fail to function properly in the event of loss of hydraulic control (due to normal system shutdown, vehicle or hydraulic system power loss, hydraulic fluid leakage, etc.) In this instance, it is desirable that the vehicle is returned to and maintains an upright (no lean) configuration until hydraulic control can be restored. It is also desirable that the configuration of the vehicle, in the absence of hydraulic control, be as stable as possible.